1. Module 3 – 3.1.2 Transport in Animals Blood Vessels and Blood By Ms Cullen

2. Blood Vessels Q Can you remember the difference between closed and open circulatory systems and examples of each?

3. Artery, vein and capillary Blood Vessels

4. Components of WallsFunction Elastic tissueAllows expansion of the lumen without causing damage. Allows elastic recoil and smooths out the flow of blood. Smooth muscleCan contract and narrow vessels, vasoconstriction, therefore reducing blood flow. It can widen vessels, vasodilation, increasing blood flow and distribution. CollagenA fibrous protein that provides strength.

5. Arteries Q What do you know about them already?

6. Arteries Endothelium folded to prevent damage as the artery stretches

7. Veins Q What do you know about them already?

8. Veins

10. Capillaries Q What do you know about them already?

11. ArteryVeinCapillary Elastic tissue in wall Smooth muscle in wall Thickness of wall Endothelium (inner lining) Presences of Valves Diameter of Lumen Copy and complete:

12. Complete Activity 14: Make annotated diagrams of blood vessels

13. Measuring blood pressure

14. The heart is made of cardiac muscle. When this muscle contracts it increases the pressure on the blood inside the heart, forcing it into the arteries that carry the blood to the body. You can feel your blood pressure when you take your pulse.

15. Measuring blood pressure Systolic Pressure - This happens when the heart is contracting. Diastolic Pressure – is the heart relaxing and the pressure in the arteries drops. A healthy 16 year old would have a blood pressure of around 120 over 80 mmHg.

16. Measuring blood pressure

17. What affects blood pressure? Diet – especially excessive amounts of salt. Age Exercise Weight Alcohol and smoking Stress

18. What Happens if you have high blood pressure? Extra strain on the heart can cause blood vessels to burst, this can damage the brain and is known as a stroke. The kidneys can be damaged causing kidney failure.

19. What Happens if you have low blood pressure? Blood is not moving as fast through your blood vessels and so less oxygen gets carried to your brain causing dizzy spells or fainting. Poor blood circulation means your fingers and toes may not get enough blood and this can harm the cells. http://ed.ted.com/lessons/how-blood-pressure-works-wilfred-manzano

20. Blood, Tissue Fluid and Lymph

21. Blood On A3 paper concept map everything you can remember from GCSE about the structure and function of blood.

22. How tissue fluid is formed The plasma of blood contains protein molecules called plasma proteins. These remain in the blood all the time. As blood flows through capillaries, some of the plasma leaks out of through the capillary walls and into the spaces between the cells in the tissue. This leaked plasma is now known as tissue fluid. Tissue fluid has a similar composition to blood plasma, but it has fewer plasma proteins as they are large molecules and it is harder for them to get through the tiny holes in the capillary endothelium. Red blood cells are also too large to get into tissue fluid, although some white blood cells can and are able to move around freely in the tissue fluid.

23. How tissue fluid is formed The amount of fluid which leaves the capillaries and forms tissue fluid is influenced by 2 opposing processes– blood pressure (hydrostatic pressure) and osmosis (oncotic pressure) Q: Where will more fluid leak out of the capillary, arteriole or venule end and why? A: arteriole as blood under higher pressure here. Tissue fluid lacks the high concentration of plasma proteins compared to blood, this creates a water potential gradient. Q: In which direction will water move and why? A: This encourages the movement of water from the tissue fluid back into the capillary. The result of these 2 opposing processes leads to a net flow out of the capillaries into the tissue fluid at the arteriole end and into the capillary at the venous end. NB: Overall, more fluid flows out than flows back in, so there is a net loss of fluid as blood passes through a capillary bed.

24. How tissue fluid is formed

25. Tissue Fluid Tissue fluid is the surrounding environment for individual cells and it is here that materials are exchanged. Many processes in the body maintain the composition of tissue fluid to a constant level. Q: What do we collectively call these processes?

26. Lymphatics Approx 90% of the fluid which leaks from capillaries will eventually go back to them. The remaining 10% is collected and returned to the blood system by a series of tubes called lymph vessels or lymphatics. These are tiny, dead-end vessels, found in almost all tissues of the body. Tissue fluid can flow into lymph vessels through valves, but can not flow out. The valves are large enough to allow large proteins through, necessary as proteins are to large to get into blood capillaries and so cannot be taken away by the blood. If your lymphatics did not take away proteins in the tissue fluid between your cells you would die within 24 hours! If the rate of loss of fluid from blood plasma is not the same as the rate of removal of tissue fluid as lymph, then there can be a build up of tissue fluid called oedema.

27. Lymph The fluid inside lymphatics is called lymph and is practically identical to tissue fluid in composition. In some tissues the lymph and tissue fluid are rather different to in other tissues. eg in the liver, lymph and tissue fluid are high in proteins. In the small intestine they are high in lipids, as this is where lipids are absorbed from digested food.

29. Lymph Lymphatics have valves to stop the lymph flowing backwards. Lymph flow is very slow, approx 100cm 3 per hour through the largest lymph vessel, the thoracic duct. In comparison blood flows approx 80cm 3 per second!

30. How Blood Carries Oxygen

31. Haemoglobin is the iron-containing oxygen-transport protein in the red cells of the blood in mammals and other animals. It transports oxygen from the lungs to the rest of the body where it releases the oxygen load. Haemoglobin is an example of a globular protein. It has 4 polypeptide chains and 4 haem groups. The haem groups (containing iron) are the site of oxygen binding. Haemoglobin

32. The Role of Haemoglobin Each haemoglobin molecule combines with 8 oxygen atoms to form oxyhaemoglobin. Q: When do you think haemoglobin combines with and releases oxygen? A: haemoglobin combines with oxygen when it is in high concentration and releases it when oxygen is in low concentrations. Therefore it picks up oxygen at the lungs and releases it at tissues. When haemoglobin releases oxygen it is called dissociation. Hb + 4O 2 HbO 8

33. Transporting Oxygen The ability of haemoglobin to take up and release oxygen depends on the amount of oxygen in the surrounding tissues. This is known as the partial pressure or pO 2. It is also known as the oxygen tension and is measured in units of pressure (kPa). In a normal liquid you would expect the amount of oxygen absorbed to be directly proportional to the oxygen tension in the surrounding air and produce a straight line on a graph. This is not the case with haemoglobin. An s-shaped or sigmoid graph is produced instead and is known as an oxygen dissociation curve.

34. Oxygen Dissociation Curve As haem is in the centre of the haemoglobin molecule, at lower pO 2 it is more difficult for oxygen molecules to reach the haem group and associate with it. As pO 2 increases the diffusion gradient increases. One molecule of oxygen diffuses into haemoglobin and associates with one of the haem groups. This changes the shape of the molecule and allows other oxygen molecules to diffuse in causing the line to be steep Once 3 oxygen molecules have associated it becomes more difficult for the 4 th. So the curve levels off as it approaches 100% saturation

36. Oxygen Dissociation Curve Remember! Oxygen associates with haemoglobin when there is high pO 2 and dissociates when the pO 2 is low. Lung tissue has a percentage O 2 saturation of 95-97% (high pO 2 ) and respiring muscle cells have a percentage O 2 saturation of 20-25% (low pO 2 )

37. Foetal haemoglobin loads and unloads oxygen at lower pO 2. The curve is to the left of adult haemoglobin, showing that foetal haemoglobin has a HIGHER affinity for oxygen. This is important in transferring oxygen from maternal Hb to foetal Hb. The placenta has a lower pO 2 allowing oxygen to dissociate from adult Hb to combine with foetal Hb. Foetal haemoglobin

39. Transport of Carbon dioxide CO 2 is transported in the blood in 3 ways: 85% as hydrogen carbonate ions mostly dissolved in the blood plasma 10% attached to haemoglobin as carbaminohaemoglobin in the erythrocytes 5% dissolved in solution in the blood plasma

40. In the lungs the CO 2 concentration is low so carbonic anhydrase catalyses the reverse reaction and free CO 2 diffuses out of the blood into the lungs.

41. Transport of Carbon dioxide in erythrocytes Some of the CO 2 diffuses into the erthrocytes. The enzyme carbonic anhydrase is present in the cytoplasm and catalyses the following reaction carbon dioxide + water carbonic acid CO 2 + H 2 0 H 2 CO 3 The carbonic acid then dissociates (splits): carbonic acid hydrogen ion + hydrogen carbonate ion H 2 CO 3 H + + HCO 3 -

42. Transport of Carbon dioxide in erythrocytes The hydrogen ions combine with the haemoglobin molecules forming haemoglobinic acid. This makes the haemoglobin release the oxygen it is carrying. The hydrogencarbonate ions diffuse out of the erythrocyte and into the blood plasma, where they remain in solution and are carried to the lungs. To balance out the diffusion of the negative hydrogencarbonate ions, chloride ions (Cl - ) diffuse in the opposite direction, from the plasma to the cytoplasm of the erthrocytes. This is called the chloride shift. Some CO 2 is not catalysed by the enzyme carbonic anhydrase and instead it combines directly with haemoglobin forming carbaminohaemoglobin.

43. In the lungs the CO 2 concentration is low so carbonic anhydrase catalyses the reverse reaction and free CO 2 diffuses out of the blood into the lungs.

44. How carbon dioxide is converted to hydrogencarbonate ions

45. The Bohr Shift Named after Christian Bohr, Danish Physiologist (1855- 1911), who discovered the effect in 1904. Cells with a high rate of respiration produce high concentrations of CO 2 and these cells need more O 2. These high CO 2 concentrations cause the haemoglobin to release their O 2 even more readily than normal. This is due to the low pH, acidity caused by haemoglobinic acid formed in the erythrocytes, which affects the structure of the haemoglobin, which is a globular protein. When more CO 2 is present, haemoglobin is less saturated with O 2. This makes the oxygen dissociation curve shift down and to the right (the Bohr shift).

47. The Bohr Effect An increase in CO 2 = an increase in O 2 released = a decrease in O 2 saturation The oxygen dissociation curve shifts more and more to the right as pCO 2 increases because this causes lowering of pH (becoming more acidic).